Clinical presentation

Effects of organophosphate and carbamate poisoning include:

CNS effects—seizures, confusion, coma
autonomic effects—acute cholinergic crisis
- cholinergic (muscarinic) toxicity—sweating, miosis, bradycardia, hypotension, salivation, lacrimation, diarrhoea, urinary frequency, bronchorrhoea, bronchoconstriction
- cholinergic (nicotinic) toxicity—muscle fasciculations, neuromuscular paralysis, hypertension, tachycardia
gastrointestinal effects—nausea, vomiting, diarrhoea; can be nonspecific effects of the solvent or pesticide, or occur as part of the acute cholinergic crisis
cardiovascular effects—bradycardia, arrhythmia, refractory shock (more common following dimethoate).

Late complications of organophosphate and carbamate poisoning include:

progressive neuromuscular junction dysfunction and respiratory failure over 1 to 4 days
pneumonia, aspiration pneumonitis.

The spectrum, onset and severity of toxic effects can vary enormously depending on the compound’s:

Properties and effects of organophosphate and carbamate pesticides provides information on the properties and effects of organophosphate and carbamate pesticides commonly available in Australia.

Table 1. Properties and effects of organophosphate and carbamate pesticides
Pesticide	Physicochemical properties	Effects
organophosphates
chlorpyrifos	diethyl-OP high fat solubility long half-life	cholinergic effects including neuromuscular paralysis
diazinon	diethyl-OP fat soluble short half-life	early cholinergic effects, but delayed neuromuscular paralysis (uncommon)
dimethoate	dimethyl-OP low fat solubility short half-life	high mortality early cholinergic effects including neuromuscular effects refractory shock
fenthion	dimethyl-OP high fat solubility long half-life	mild initial cholinergic effects followed by delayed neuromuscular effects (24 to 96 hours)
profenofos	S-alkyl-OP moderate fat solubility long half-life	severe initial cholinergic effects prolonged respiratory failure
malathion	dimethyl-OP moderate fat solubility short half-life	typical cholinergic effects lower toxicity (except in large ingestions)
carbamates
carbamates	do not require metabolic conversion for activity short half-life	rapid onset of cholinergic effects, followed by recovery over 1 to 2 days delayed respiratory failure (uncommon)
Note: OP = organophosphate